The invention relates to a magnetic-tape cassette apparatus, which comprises a magnetic head unit equipped with a magnetic head having a head face in which a head gap terminates, along which head face a magnetic tape is passed. The magnetic head unit carries height limiters disposed on opposite sides of the head gap in the direction of transport of the magnetic tape, for limiting movement of the magnetic tape in at least one direction.
In magnetic-tape casset apparatuses of this kind the tape path is partly defined by elements on the apparatus and partly by tape guides arranged in the magnetic-tape cassette. These tape guides, which are generally mass-manufactured from a plastic material, are subject to fairly large tolerances. In practice it is mainly these tolerances which give rise to so-called azimuth errors in magnetic-tape cassette apparatuses; that is, errors which occur because the head-gap position deviates from a purely perpendicular position to the longitudinal edge of the magnetic tape. For example, during stereo reproduction a deviation of 20 minutes may give rise to a loss of 10 dB at a frequency of 10 kHz. This is particularly undesirable when pre-recorded magnetic-tape cassettes, so-called music cassettes, are played back.
In order to solve this problem is has been proposed to utilize control systems which, for example by means of piezo-electric elements, constantly influence the lace-up so as to cancel any azimuth errors. Such control systems cause the cassette apparatus to be very expensive and in fact do not provide a satisfactory general solution.